Question

1. How do we know that the global mean temperature is increasing unusually fast? Besides the temperature itself, list at least 4 other observations that indicate a warming climate.

2. How do we know that the CO2 content of the atmosphere has increased over the past few decades?

Answer 1

1)

Earth-orbiting satellites and other technological advances have enabled scientists to see the big picture, collecting many different types of information about our planet and its climate on a global scale. This body of data, collected over many years, reveals the signals of a changing climate.

Warming Oceans -

The oceans have absorbed much of the increased heat, with the top 700 meters (about 2,300 feet) of ocean showing warming of more than 0.4 degrees Fahrenheit since 1969.

• Shrinking Ice Sheets - The Greenland and Antarctic ice sheets have decreased in mass. Data from NASA's Gravity Recovery and Climate Experiment show Greenland lost an average of 286 billion tons of ice per year between 1993 and 2016, while Antarctica lost about 127 billion tons of ice per year during the same time period. The rate of Antarctica ice mass loss has tripled in the last decade.

• Glaciers are retreating almost everywhere around the world — including in the Alps, Himalayas, Andes, Rockies, Alaska and Africa.

• Both the extent and thickness of Arctic sea ice has declined rapidly over the last several decades.

• Decreased Snow Cover - Satellite observations reveal that the amount of spring snow cover in the Northern Hemisphere has decreased over the past five decades and that the snow is melting earlier.

• SEA LEVEL RISE - Global sea level rose about 8 inches in the last century. The rate in the last two decades, however, is nearly double that of the last century and is accelerating slightly every year.

• OCEAN ACIDIFICATION - Since the beginning of the Industrial Revolution, the acidity of surface ocean waters has increased by about 30 percent. This increase is the result of humans emitting more carbon dioxide into the atmosphere and hence more being absorbed into the oceans.

2)

current level carbon dioxide level (parts per million) For millennia, atmospheric carbon dioxide had never been above this line, – 1950 level 280 260 160 800,000 700,000 600,000 200,000 100,000 500,000 400,000 300,000 years before today (0 = 1950) climate.nasa.gov